gecko/toolkit/devtools/DevToolsUtils.js

401 lines
11 KiB
JavaScript

/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
/* General utilities used throughout devtools. */
// hasChrome is provided as a global by the loader. It is true if we are running
// on the main thread, and false if we are running on a worker thread.
var { Ci, Cu } = require("chrome");
var Services = require("Services");
var { setTimeout } = require("Timer");
/**
* Turn the error |aError| into a string, without fail.
*/
exports.safeErrorString = function safeErrorString(aError) {
try {
let errorString = aError.toString();
if (typeof errorString == "string") {
// Attempt to attach a stack to |errorString|. If it throws an error, or
// isn't a string, don't use it.
try {
if (aError.stack) {
let stack = aError.stack.toString();
if (typeof stack == "string") {
errorString += "\nStack: " + stack;
}
}
} catch (ee) { }
// Append additional line and column number information to the output,
// since it might not be part of the stringified error.
if (typeof aError.lineNumber == "number" && typeof aError.columnNumber == "number") {
errorString += "Line: " + aError.lineNumber + ", column: " + aError.columnNumber;
}
return errorString;
}
} catch (ee) { }
return "<failed trying to find error description>";
}
/**
* Report that |aWho| threw an exception, |aException|.
*/
exports.reportException = function reportException(aWho, aException) {
let msg = aWho + " threw an exception: " + exports.safeErrorString(aException);
dump(msg + "\n");
if (Cu.reportError) {
/*
* Note that the xpcshell test harness registers an observer for
* console messages, so when we're running tests, this will cause
* the test to quit.
*/
Cu.reportError(msg);
}
}
/**
* Given a handler function that may throw, return an infallible handler
* function that calls the fallible handler, and logs any exceptions it
* throws.
*
* @param aHandler function
* A handler function, which may throw.
* @param aName string
* A name for aHandler, for use in error messages. If omitted, we use
* aHandler.name.
*
* (SpiderMonkey does generate good names for anonymous functions, but we
* don't have a way to get at them from JavaScript at the moment.)
*/
exports.makeInfallible = function makeInfallible(aHandler, aName) {
if (!aName)
aName = aHandler.name;
return function (/* arguments */) {
try {
return aHandler.apply(this, arguments);
} catch (ex) {
let who = "Handler function";
if (aName) {
who += " " + aName;
}
exports.reportException(who, ex);
}
}
}
/**
* Interleaves two arrays element by element, returning the combined array, like
* a zip. In the case of arrays with different sizes, undefined values will be
* interleaved at the end along with the extra values of the larger array.
*
* @param Array a
* @param Array b
* @returns Array
* The combined array, in the form [a1, b1, a2, b2, ...]
*/
exports.zip = function zip(a, b) {
if (!b) {
return a;
}
if (!a) {
return b;
}
const pairs = [];
for (let i = 0, aLength = a.length, bLength = b.length;
i < aLength || i < bLength;
i++) {
pairs.push([a[i], b[i]]);
}
return pairs;
};
/**
* Waits for the next tick in the event loop to execute a callback.
*/
exports.executeSoon = function executeSoon(aFn) {
Services.tm.mainThread.dispatch({
run: exports.makeInfallible(aFn)
}, Ci.nsIThread.DISPATCH_NORMAL);
};
/**
* Waits for the next tick in the event loop.
*
* @return Promise
* A promise that is resolved after the next tick in the event loop.
*/
exports.waitForTick = function waitForTick() {
let deferred = promise.defer();
exports.executeSoon(deferred.resolve);
return deferred.promise;
};
/**
* Waits for the specified amount of time to pass.
*
* @param number aDelay
* The amount of time to wait, in milliseconds.
* @return Promise
* A promise that is resolved after the specified amount of time passes.
*/
exports.waitForTime = function waitForTime(aDelay) {
let deferred = promise.defer();
setTimeout(deferred.resolve, aDelay);
return deferred.promise;
};
/**
* Like Array.prototype.forEach, but doesn't cause jankiness when iterating over
* very large arrays by yielding to the browser and continuing execution on the
* next tick.
*
* @param Array aArray
* The array being iterated over.
* @param Function aFn
* The function called on each item in the array. If a promise is
* returned by this function, iterating over the array will be paused
* until the respective promise is resolved.
* @returns Promise
* A promise that is resolved once the whole array has been iterated
* over, and all promises returned by the aFn callback are resolved.
*/
exports.yieldingEach = function yieldingEach(aArray, aFn) {
const deferred = promise.defer();
let i = 0;
let len = aArray.length;
let outstanding = [deferred.promise];
(function loop() {
const start = Date.now();
while (i < len) {
// Don't block the main thread for longer than 16 ms at a time. To
// maintain 60fps, you have to render every frame in at least 16ms; we
// aren't including time spent in non-JS here, but this is Good
// Enough(tm).
if (Date.now() - start > 16) {
exports.executeSoon(loop);
return;
}
try {
outstanding.push(aFn(aArray[i], i++));
} catch (e) {
deferred.reject(e);
return;
}
}
deferred.resolve();
}());
return promise.all(outstanding);
}
/**
* Like XPCOMUtils.defineLazyGetter, but with a |this| sensitive getter that
* allows the lazy getter to be defined on a prototype and work correctly with
* instances.
*
* @param Object aObject
* The prototype object to define the lazy getter on.
* @param String aKey
* The key to define the lazy getter on.
* @param Function aCallback
* The callback that will be called to determine the value. Will be
* called with the |this| value of the current instance.
*/
exports.defineLazyPrototypeGetter =
function defineLazyPrototypeGetter(aObject, aKey, aCallback) {
Object.defineProperty(aObject, aKey, {
configurable: true,
get: function() {
const value = aCallback.call(this);
Object.defineProperty(this, aKey, {
configurable: true,
writable: true,
value: value
});
return value;
}
});
}
/**
* Safely get the property value from a Debugger.Object for a given key. Walks
* the prototype chain until the property is found.
*
* @param Debugger.Object aObject
* The Debugger.Object to get the value from.
* @param String aKey
* The key to look for.
* @return Any
*/
exports.getProperty = function getProperty(aObj, aKey) {
let root = aObj;
try {
do {
const desc = aObj.getOwnPropertyDescriptor(aKey);
if (desc) {
if ("value" in desc) {
return desc.value;
}
// Call the getter if it's safe.
return exports.hasSafeGetter(desc) ? desc.get.call(root).return : undefined;
}
aObj = aObj.proto;
} while (aObj);
} catch (e) {
// If anything goes wrong report the error and return undefined.
exports.reportException("getProperty", e);
}
return undefined;
};
/**
* Determines if a descriptor has a getter which doesn't call into JavaScript.
*
* @param Object aDesc
* The descriptor to check for a safe getter.
* @return Boolean
* Whether a safe getter was found.
*/
exports.hasSafeGetter = function hasSafeGetter(aDesc) {
let fn = aDesc.get;
return fn && fn.callable && fn.class == "Function" && fn.script === undefined;
};
/**
* Check if it is safe to read properties and execute methods from the given JS
* object. Safety is defined as being protected from unintended code execution
* from content scripts (or cross-compartment code).
*
* See bugs 945920 and 946752 for discussion.
*
* @type Object aObj
* The object to check.
* @return Boolean
* True if it is safe to read properties from aObj, or false otherwise.
*/
exports.isSafeJSObject = function isSafeJSObject(aObj) {
if (Cu.getGlobalForObject(aObj) ==
Cu.getGlobalForObject(exports.isSafeJSObject)) {
return true; // aObj is not a cross-compartment wrapper.
}
let principal = Cu.getObjectPrincipal(aObj);
if (Services.scriptSecurityManager.isSystemPrincipal(principal)) {
return true; // allow chrome objects
}
return Cu.isXrayWrapper(aObj);
};
exports.dumpn = function dumpn(str) {
if (exports.dumpn.wantLogging) {
dump("DBG-SERVER: " + str + "\n");
}
}
// We want wantLogging to be writable. The exports object is frozen by the
// loader, so define it on dumpn instead.
exports.dumpn.wantLogging = false;
/**
* A verbose logger for low-level tracing.
*/
exports.dumpv = function(msg) {
if (exports.dumpv.wantVerbose) {
exports.dumpn(msg);
}
};
// We want wantLogging to be writable. The exports object is frozen by the
// loader, so define it on dumpn instead.
exports.dumpv.wantVerbose = false;
exports.dbg_assert = function dbg_assert(cond, e) {
if (!cond) {
return e;
}
}
/**
* Utility function for updating an object with the properties of another
* object.
*
* @param aTarget Object
* The object being updated.
* @param aNewAttrs Object
* The new attributes being set on the target.
*/
exports.update = function update(aTarget, aNewAttrs) {
for (let key in aNewAttrs) {
let desc = Object.getOwnPropertyDescriptor(aNewAttrs, key);
if (desc) {
Object.defineProperty(aTarget, key, desc);
}
}
}
/**
* Defines a getter on a specified object that will be created upon first use.
*
* @param aObject
* The object to define the lazy getter on.
* @param aName
* The name of the getter to define on aObject.
* @param aLambda
* A function that returns what the getter should return. This will
* only ever be called once.
*/
exports.defineLazyGetter = function defineLazyGetter(aObject, aName, aLambda) {
Object.defineProperty(aObject, aName, {
get: function () {
delete aObject[aName];
return aObject[aName] = aLambda.apply(aObject);
},
configurable: true,
enumerable: true
});
};
/**
* Defines a getter on a specified object for a module. The module will not
* be imported until first use.
*
* @param aObject
* The object to define the lazy getter on.
* @param aName
* The name of the getter to define on aObject for the module.
* @param aResource
* The URL used to obtain the module.
* @param aSymbol
* The name of the symbol exported by the module.
* This parameter is optional and defaults to aName.
*/
exports.defineLazyModuleGetter = function defineLazyModuleGetter(aObject, aName,
aResource,
aSymbol)
{
this.defineLazyGetter(aObject, aName, function XPCU_moduleLambda() {
var temp = {};
Cu.import(aResource, temp);
return temp[aSymbol || aName];
});
};